I need to add a quart but don't want to go to the dealer ... best option recommended?

Buy the oil and add it yourself.

My car with 19,000km and last oil change 7,000km ago, just asked me for a quart last night. The orange oil symbol appeared on the DIC and there was a warning that oil level is at minimum. I stopped, added the oil, and drove away. 15 minutes later, the level was measured 1/8 from full. Problem solved.

The thing I like about BMW is that they foresee stupid little things. I bought a carrying case (for a quart) from BMW and it came with two paper funnels and a alcohol wetnap inside. Thank you BMW.